Dual cure cyanate ester inkjet composition

Abstract

The present invention relates to an inkjet composition having 1.0-5.0 mol/kg acryloyl groups comprising: i) photo polymerization reactive compound (M) containing exactly one acryloyl group, ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, iii) radical photoinitiator (R), iv) cyanate ester compound (D) containing at least two cyanate groups and v) cyanate ester curing catalyst (C), wherein (M) is different from (D) and (N) is different from (D), 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95.

The invention claimed is: 
     
       1. An inkjet composition comprising:
 i) photo polymerization reactive compound (M) containing exactly one acryloyl group, 
 ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, 
 iii) radical photoinitiator (R), 
 iv) cyanate ester compound (D) containing at least two cyanate groups, and 
 v) cyanate ester curing catalyst (C), wherein 
 (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), 
 (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 
 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95, and 
 the inkjet composition has 1.0-5.0 mol/kg acryloyl groups. 
 
     
     
       2. The inkjet composition according to  claim 1  having 1.7-3.5 mol/kg acryloyl groups. 
     
     
       3. The inkjet composition according to  claim 1  30-45 mol % of the contained acryloyl groups are provided by the reactive compound (N). 
     
     
       4. The inkjet composition according to  claim 1 , wherein 80-100 mol % of the reactive compound (N) are species containing not more than three acryloyl groups. 
     
     
       5. The inkjet composition according to  claim 1 , wherein the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.36 to 0.94. 
     
     
       6. The inkjet composition according to  claim 1 , wherein at least 30 wt.-% of the species of (D) are 4,4′-ethylidenediphenyl dicyanate. 
     
     
       7. The inkjet composition according to  claim 1 , wherein the radical photoinitiator (R) comprises a phosphinoxide-based photoinitiator. 
     
     
       8. The inkjet composition according to  claim 1 , wherein the cyanate ester curing catalyst (C) comprises an aluminum metal catalyst. 
     
     
       9. The inkjet composition according to  claim 1 , wherein 90-100 wt. % of the contained ingredients are species of (M), (N), (R), (D) and (C). 
     
     
       10. The inkjet composition according to  claim 1 , having a viscosity of 10-40 mPa s at 45° C., where the viscosity is measured on a thermally controlled rotational rheometer in cone-plate geometry, cone diameter: 60 mm, zero-gap distance: 0,061 mm, cone angle: 0,5°, shear-rate 600s-1, at temperatures from 40 to 60° C. with a heating ramp of 2 K/min following the DIN EN ISO 3219. 
     
     
       11. The inkjet composition according to  claim 1 , which does not contain cationic or anionic (photo) polymerization initiator. 
     
     
       12. The inkjet composition according to  claim 1 , which contains less than 6 wt. % radical polymerizable monomers not containing acryloyl groups. 
     
     
       13. The inkjet composition according to  claim 1 , additionally containing one or more of a stabilizer, a wetting agent, a defoamer, a radical polymerization inhibitor, and a pigment. 
     
     
       14. A process for printing a three-dimensional object comprising the steps of:
 (a) jetting an inkjet composition by means of a printing machine to form a layer in a configured pattern corresponding to the shape of the object, the inkjet composition comprising: 
 i) photo polymerization reactive compound (M) containing exactly one acryloyl group, 
 ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, 
 iii) radical photoinitiator (R), 
 iv) cyanate ester compound (D) containing at least two cyanate groups, and 
 v) cyanate ester curing catalyst (C), wherein 
 (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), 
 (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 
 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.95, and 
 the inkjet composition has 1.0-5.0 mol/kg acryloyl groups 
 (b) irradiating the formed layer to form a photo-cured layer, 
 (c) sequentially repeating steps (a) and (b) to form a plurality of photo-cured layers in order to prepare a green body of the three-dimensional object, and 
 (d) heating the green body to post cure the three-dimensional object. 
 
     
     
       15. The process according to  claim 14 , further comprising printing and curing a support ink to stabilize the green body, and removing the cured support ink after step c) and before the performance of step (d) by treating with an aqueous washing liquid, wherein the cured support ink is water soluble. 
     
     
       16. The process according to one  claim 14 , wherein the heating step (d) is performed in such a way that temperatures between 11° and 140° C. are kept at least for 5 hours. 
     
     
       17. The process according to  claim 16 , wherein in the heating step (d) the relevant increase of the temperature is limited to 2 K/min. 
     
     
       18. The process according to  claim 14 , wherein in step (b) the irradiation is performed by means of an UV lamp and the exposure time of each ink layer is 0.1-2 s. 
     
     
       19. A three-dimensional object manufactured according to the process according to  claim 14 . 
     
     
       20. A three-dimensional object manufactured from an inkjet composition comprising:
 i) photo polymerization reactive compound (M) containing exactly one acryloyl group, 
 ii) photo polymerization reactive compound (N) containing at least two acryloyl groups, 
 iii) radical photoinitiator (R), 
 iv) cyanate ester compound (D) containing at least two cyanate groups, and 
 v) cyanate ester curing catalyst (C), wherein 
 (M) is different from (D) with the proviso that cyanate ester compound containing exactly one acryloyl group and additionally containing at least two cyanate groups is subsumed to (D), 
 (N) is different from (D) with the proviso that cyanate ester compound containing at least two acryloyl groups and additionally containing at least two cyanate groups is subsumed to (D), 
 25-50 mol % of the contained acryloyl groups are provided by the reactive compound (N) and the molar ratio of contained acryloyl groups to contained cyanate groups of compound (D) is 0.30 to 0.9, and 
 the inkjet composition has 1.0-5.0 mol/kg acryloyl groups. 
 
     
     
       21. The inkjet composition according to  claim 1 , wherein 90-100 mol % of the reactive compound (N) are species containing not more than three acryloyl groups. 
     
     
       22. The inkjet composition according to  claim 1 , wherein least 60 wt.-% of the species of (D) are 4,4′-ethylidenediphenyl dicyanate. 
     
     
       23. The inkjet composition according to  claim 1 , wherein the radical photoinitiator (R) comprises diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide and/or phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide. 
     
     
       24. The inkjet composition according to  claim 1 , wherein the cyanate ester curing catalyst (C) comprises aluminum acetylacetonate. 
     
     
       25. The inkjet composition according to  claim 1 , wherein 97-100 wt. % of the contained ingredients are species of (M), (N), (R), (D) and (C). 
     
     
       26. The inkjet composition according to  claim 1 , which contains less than 2 wt. % radical polymerizable monomers not containing acryloyl groups.